LEGISLATIVE REFERENCE LIBRARY 1 f lilliill b !li1i~ll~~3 0307 ~l~lll! 00045 li~lllllf 9597l~~l~i POSSIBLE ENVIRON ENTAL I PA CT OF _BASE ET AL ININ6 IN INNESOTA MINNESOTA DEPARTMENT OF NATURAL RESOURCES DIVISION OF WATERS, SOILS & MINERALS JUNE 1972 This document is made available electronically by the Minnesota Legislative Reference Library as part of an ongoing digital archiving project. http://www.leg.state.mn.us/lrl/lrl.asp (Funding for document digitization was provided, in part, by a grant from the Minnesota Historical & Cultural Heritage Program.) STATE OF MINNESOTA DEPARTMENT OF NATURAL RESOURCES DIVISION OF WATERS, SOILS AND MINERALS POSSIBLE ENVIRONMENTAL IMPACT OF BASE METAL MINING IN MINNESOTA By William C. Brice 345 Centennial Office Building St. Paul, Minnesota 55155 TABLE OF CONTENTS Page SCOPE AND PURPOSE 1 BASE METAL MINING IN MINNESOTA 1 Markets Mining Methods Beneficiation 4 Metal Extraction 6 Refining 7 AIR POLLUTION PROBLEMS ASSOCIATED WITH PYROMETALLURGICAL EXTRACTION 7 ALTERNATIVE EXTRACTION METHODS 10 Pyrometallurgical Methods 10 Hydrometallurgical Methods 10 Combination Methods 10 Comparison of Extraction Methods for Use in Minnesota 10 APPENDIX I: FUTURE MARKETS FOR COPPER-NICKEL RESOURCES 11 APPENDIX II: UNDERGROUND MINING METHODS 13 APPENDIX Ill: BENEFICIATION OF SULFIDE ORES 13 APPENDIX IV: ASSUMPTIONS USED IN THE VARIOUS CALCULATIONS 14 APPENDIX V: PYROMETALLURGICAL EXTRACTION - TRADITIONAL METHOD 15 APPENDIX VI: HYDROMETALLURGICAL EXTRACTION - LEACHING METHOD 17 APPENDIX VII: REFINING 21 APPENDIX VIII: DUST RECOVERY 21 APPENDIX IX: EFFECTS OF S02 IN THE ATMOSPHERE 21 APPENDIX X: AIR POLLUTION POTENTIAL 22 APPENDIX XI: WIND STATISTICS FOR NORTHEASTERN MINNESOTA 23 APPENDIX XII: THE TALL STACK APPROACH 26 APPENDIX XIII: SULFUR RECOVERY SYSTEMS 42 APPEND1X XIV: CURTAILED PRODUCTION 44 APPENDIX XV: PYROMETALLURGICAL EXTRACTION - Al TERNATE METHODS 44 I APPENDIX XVI: HYDROMETALLURGICAL EXTRACTION - RESEARCH 46 APPENDIX XVII: HYDROMETALLURGICAL EFFECTS AND CONTROL 52 APPENDIX XVIII: COMBINATION PYROMETALLURGICAL - HYDROMETALLURGICAL EXTRACTION RESEARCH 52 APPENDIX XIX: A CAPSULE VIEW OF U.S. COPPER SMELTING CAPABILITY 53 APPENDIX XX: CALCULATIONS OF NECESSARY RESERVES FOR THE VARIOUS EXTRACTION METHODS 55 APPENDIX XXI: CALCULATIONS OF SULFUR RECOVERY COSTS WITH THE VARIOUS EXTRACTION PROCESSES 56 APPENDIX XXll: A REVIEW OF SEVERAL MINING COMPANIES' POLLUTION CONTROL PROGRAMS 57 FIGURES AND TABLES Figure No. Page 1 Minnesota Greenstone and Gabbro Formations 2 2 Greenstone Belts of Canada and the United States 3 3 Lands Included in the Shipstead-Newton-Nolan Act 5 4 Surface Wind Roses for Northeastern Minnesota 9 5 Cutaway View of a Fluid Bed Roaster 16 6 Cutaway View of I NCO Reverberatory Furnace 18 7 Cutaway View of a Horizontal Side-blown Converter 19 8 High Pressure System and Temperature Inversion Graph 24 9 Forecast of Yearly Air Pollution Potential Episodes 25 10 Location Map for Surface Wind Roses 27 11 Key to Wind Rose Data Sheets 28 12 Influence of Vertical Temperature Variations on Stack Effluents 41 13 Generalized Citrate Process Flowsheet 43 14 Noranda Continuous Smelting Furnace 45 15 WORCRA Continuous Furnace 45 16 Cutaway View of INCO Oxygen Flash Smelting Furnace 47 17 Cutaway View of Outokumpu Flash Smelting Furnace 48 18 Cutaway View of a Blast Furnace for Sulfide Nickel Ore 49 19 Cutaway View of a Submerged Arc Electric Furnace .50 Table No. 1 Estimate of Water Requirements and Waste Products 7 2 Summary of Possible Extraction Methods and Estimate of Environmental Costs 12 3 Upper Wind Statistics for Northeastern Minnesota 26 SCOPE AND PURPOSE to review the production and recovery methods that might conceivably be used and some of the environmental and Minnesota is on the threshold of a new mining industry; production problems that could be associated with these that of copper, nickel, and other associated metals. Such processes. an industry could have a substantial impact on the economy and on the natural environment of the state depending upon the mining and processing methods utilized, and the Markets individual circumstances associated with a specific operation. Markets, although not dfrectly associated with the The .purpose of this report is to review and summarize environmental aspects of base metal mining, are important available information on the mining and processing of base because of the by-product sulfur that must be produced, metals, such as copper and nickel, in order to provide a and the fact that the total production costs of the metals guide for planning and evaluating the impact of future will have to include the recovery and sale or storage of a mining operations in Minnesota. The report emphasizes major portion of the contained sulfur. Appendix I contains advantages, disadvantages, and possible utilization of particu­ a brief review of the market outlook for copper, nickel and lar systems, and contains information on probable major sulfur. For copper, economists predict a surplus throughout environmental factors to be considered in base metal most of the seventies, and early eighties. Prices, however, operations. Background information is included in the are not expected to drop below forty-five cents per pound appendices and a bibliography is provided to assist those of copper. Expanding niclffi markets have caused a nickel wishing to study the subject further. shortage throughout most of the sixties. However, additional This report was prepared through the cooperation and productio~ capacity coupled with a slowdown in economic assistance of the United States Bureau of Mines, State Land growth rates of consuming nations has recently caused an and Forestry Offices, Superior National Forest Office and oversupply of nickel on the World market. If all of the planned United States Department of Commerce, National Weather production capacity goes on line, then the oversupply will Service Forecast Office. probably continue throughout most of the seventies. Because of the many new sources of ~lfur, this market BASE METAL MINING IN MINNESOTA appears to be in for a long period of surplus. In Minnesota, The primary potential for base metal mining in the demand for elemental sulfur and sulfuric acid is limited. Minnesota exists in the Duluth Gabbro Complex, which lies If little or no local market is found for sulfuric acid, and it north of Duluth in the "Arrowhead Country", and the appears this will be the case, then the contained sulfur Greenstone formations which cover substantial portions of would have to be recovered in a storable form, either Northern Minnesota. A geologic map showing the generalized as elemental sulfur or gypsum. location of these two formations is contained in Figure 1. In view of the concerted effort presently being made in Mining Methods Minnesota and the productivity of similar explored forma­ tions just to the north in Canada, base metal mining in Base metal mining will be substantially different than Minnesota would appear to be only a matter of time. Based the present iron ore mining we are familiar with in Northern on exploration to date, the United States Bureau of Mines Minnesota. Although portions of some ore bodies might lists the Duluth Gabbro Complex, which contains copper be amenable 1 to open pit mining, the majority would and nickel, as the largest known nickel sulfide resource probably be mined by underground methods due to the in the United Statesl. In addition, considerable exploration characteristics of the formations. Deposits in the Greenstone is being conducted in the Greenstone belts of Minnesota formation may dictate rather small underground operations, for mineral deposits containing such metals as copper, whereas deposits in the Duluth Gabbro formation may zinc, lead, gold and silver. This formation is a major support larger scale underground mines and possibly some source of Canada's mineral wealth, as shown in Figure· 2. open pit mines. Any open pit mines would be limited to In order to study the environmental aspects of future the areas adjacent to the base of the Gabbro formation where sulfide mining in Minnesota, and in particular the metal the formation is rather shallow in depth and the stripping extraction phase of such an operation, it is necessary ratio small. I I I i f-!-~~------j ! i -·-·-·-·-' I ST. LOUIS i I ~I r-·-------· I ) ~ ~ . · -~I~ ts> I i, ·v'~ I b.~Q!! ____ _ ~CASS .1 I I .... :·::.:~.1::-: ...:.-- .. ·.:~·-:·.-:::·-:·:·~--~·.:-· ~ r---~ L_____ 1. ·.·:.: ... i~~·ir~ .-:;_:-::..-·: F / \CP.OW WING 1 1Al~N 1 IRON FORMATION : ~ .. ~_ .....;;.:~~.!,_-~·;: ·-·---, i ti -·--·-·-1 1-·-·-1 .. I i · · L I I 1 1GRANT ,·.0"G •. 1,.,0.. 11·MOP.P.l~r:!.._ ____ __1 1- r GREENSTONE BELTS -·--·----.L"----·-·-·--·-·~. I /KANABEC IPIN"E 1 I I ' I ·-·-·----- T_~Y.£8.~ __ I I i { .,MILLE I 1, i l 1 \~.!!!."I2...~--~~.L - . l DULUTH GABBRO COMPLEX l22.~~~--1~PE /STEARNS \}-. jrsANTI i BIG / -----i-·-·--- J s~_RsuP.NE ---·-·-. 1 s T.~.E 1. I 1-·---i-r~· '-.--..."\i1 F~~-0 1 '""' '-f~L-._·-·-1 1 I .f".r' "·".ANOKA i DIABASIC GABBRO AND \. j ., ·-·-·1~ . I. I I~ ,_ RELATED ROCKS '-\_ I IMEEKEJL __ 1~~.!.§Ji.L_I '-t~ I~ __).~_HIPP~~h~~H_!.__l_ __ I l l!!i~~PIN \5-- j~ ~-~.lL'Y.~_u_J \,_ I I I 1-.----. / 1i ~- __,M<LE<?L_l~_RVER (° ( ,__,.... n.'=-l.QE MfQ_!_c,_uu:_ I''"' I I I 1-· ./ I I I i ·'-...RENVILLE I -·-· ,.,;;·..J.r -1 I · ,--- '"""'-."--.. j~·Q.!·~----jOAKOTA_J- . J"\,._lill.uL. ____ -<. I ·---r 1. I "'-.NICOLLET / I I I I 1· ............ ,_ ~ . I . 1· ,--·-· \ "i'.e suEuR ! I · ~~-~.!:.2'._92!._I ____ ~~~~~~- f'·---.. j-=·-1 /RICE 'GOODHUE lwABASHA ·-· I I /eAowN . .,_....:, -:-·-·-·-·-·-·-·-·-·--·-[ I ! I ·---,-·-·-·-1 I I I I ---·, I ! I I0 I i i I I ~.!f..~.~I.O.!!tlr-l!BB.~.---'f2l!~~QQ_j~_TONWAN /8LUE EARTH iwASECA ]'STEELE ioooGE ioLMS!fP. ___b'!.2.~---·-· ' 1 1 ----- -,-------·-r·----·-r-·---.~--r 1 I I I I i i i ! I I i i i I I I ROCK NOBLES JACKSON MARTIN FARIBAULT FREEBORN MOWER FILLMORE HOUSTON Figure 1 Minnesota Greenstone & Gabbro Formations 2 C> ~··,·.:····•• @: ~ ~ / .